Electrical connectors for resistance elements on glass plates



May 24, 1955 T. w. GLYNN 2,709,211

ELECTRICAL CONNECTORSFOR RESISTANCE ELEMENTS 0N GLASS PLATES Filed May 27, 1953 Lin-mm I) .a k gsETxgalb A mv 25 I Zi /VENTOR.

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United States Patent 0 ELECTRICAL CONNECTORS FOR RESISTANCE ELEMENTS ON GLASS PLATES Theodore W. Glynn, Kingsport, Tenn., assiguor to Blue Ridge Glass Corporation, Kingsport, Tenn., a corporation of New York Application May 27, 1953, Serial No. 357,671

8 Claims. (Cl. 201-63) This invention relates to electric resistance heaters in which electric heating elements cover one side of ternpered glass plates, and more particularly to the electrical terminals for such heaters.

In such a heater a very thin layer of a suitable electrical resistance material adhering to a glass plate forms a heating element strip, and connectors are fastened to the opposite ends of the element so that it can readily be connected in an electric circuit. Connectors that are suitable for this purpose are shown in my copending patent application, Serial Number 235,236, filed July 5, 1951, now Patent No. 2,644,066, dated June 30, 1953. in that application the connector has a metal disc or base that is soldered to an end of an electric heating element. The metal of the connector has substantially the same coefiicient of expansion as the glass plate in the temperature range in which the heater operates. Therefore, when the heated glass plate expands, the heated connector expands at the same rate and does not loosen. The connectors shown in my copending patent application are perfectly satisfactory, but it sometimes is desirable to use a spade type of connector which has a tongue over which a sleeve-like terminal can be slid. The terminal is connected to a wire that supplies electricity to the heater. The difficulty with a spade type connection is that during and after the manufacture of the heater the tongues of the connectors are bent toward and away from the glass plate, with the result that the bases of the connectors are pulled loose from the plate or the resistance of the tongues to bending causes the bases to fracture the surface of the glass.

It is among the objects of this invention to provide in an electric resistance heater of the type described, an electrical connector having a projecting tongue that can be bent without loosening the connector and without injuring the surface of the glass. In accordance with this invention the inner face of the connector base is soldered to one end of the electrical heating element adhering to the glass plate. The connector has an integral tongue that is struck out of the base and projects from its outer face for slidably receiving a sleeve that is fastened to a wire of the supply circuit. The outer end of the tongue is free, but its inner end is joined to the base of the connector. The tongue is reduced in cross sectional area a short distance from the base in order to weaken the tongue at that point. Consequently, if-pressure is applied to the tongue either toward oraway from the base it will bend the tongue at its weakened point and not loosen the base from the glass plate or cause the base to fracture the surface of the plate.

This invention is illustrated in the accompanying drawings, in which:

Fig. l is a fragmentary view of one side of an electric resistance heater utilizing my electrical connectors;

Fig. 2 is an enlarged detail showing a connector;

Fig. 3 is a vertical section taken on the line III-III of Fig. 2;

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Fig. 4 is a perspective view of the connector, and

Figs. 5 and 6 are plan views of further embodiments; and

Fig. 7 is a side view of another modification.

Referring to Figs. 1 to 4 of the drawings, a rectangular panel or plate 1 of tempered glass, of the kind used for an electric resistance type of space heater, is shown. Mounted on one side of the glass plate is an electric heating element 2 which is formed from at least one electrical conductor that has its ends 3 enlarged and located close to each other. The ends preferably are at the bottom of the plate, substantially midway between its ends. The conductor is formed from suitable electrical resistance material, generally aluminum or aluminum alloy, sprayed on the surface of the plate in a very thin strip. On the larger terminal areas 3 of the heating element an additional coating 4 or a solderable metal, such as copper or brass or zinc, has been sprayed because it is difiicult to solder directly to the thin aluminum areas.

The bases 6 of a pair of metal connectors are joined to the coatings 4 by an ordinary high melting point leadtin solder 7 (Fig. 3). This was done by first tinning the coatings 4 and the inner faces or backs of the connector bases with the solder and then clamping the bases against the tinned areas of the resistance element. The entire assembly then was heated to the melting point of the solder to make a sweat joint between the connectors and plate. With both the plate and the connectors at the same temperature at the time of fusion of solder 7, and with both being cooled down together, the final joints are free from shrinkage stress and will remain that way in service.

The material of which the connectors are made is a low expansion metal having substantially the same coefficient of expansion as the glass plate in the temperature range in which the heater operates, which is from about 32 F. to about 300 F. Consequently, the connector bases will expand and contract with the plate at the same rate. An example of a preferred metal alloy having the proper coefficient of expansion is one composed of about 48% nickel and about 52% iron. Although the solder 7 has a much greater coefficient of expansion than the plate and connector, it does not pull loose because it is a very thin layer and has low tensile strength. The film of solder is simply stretched or compressed by the glass plate and metal connectors on its opposite sides as they become hot or cold. The same thing is true of the thin tinned areas of the resistance element, which also are sandwiched in between the connectors and plate.

The central portion of the base of each connector is struck-out by a punch to provide a spade or tongue 9 that preferably is rectangular. The inner end of the tongue, of course, is integral with the base at one end of the opening 10 left by the tongue. A short length of the tongue at its inner end extends away from the base at a rather sharp angle, but the rest of the tongue is bent back toward the base so that most of the tongue extends at an angle of less than 20 degrees to the base. With the tongue disposed at an angle, it is easy to slide onto it a sleeve-like terminal 11 of well known construction which is connected to a wire 12 that supplies electric current to the heating element. This terminal is not a complete sleeve, but has its opposite edges turned in to press against the tongue in order to make a good electrical connection.

Connectors formed as described thus far often pulled loose from the plate or caused minute cracks or frac tures in the surface of the plate, which later enlarged and shortened the life of the plate. it has been found that those disadvantages occurred because of forces which bent orvattempted to bend the connector tongues. The tongues, instead of bending or along with their bending,

separated the connectors from the glass plate or caused the ends of the connector bases to cut into or fracture the surface of the plate. The damaging pressure on the tongues occurs during and following the heater manufacturing process. Thus, after the connector bases have been soldered in place, the plate is etched, which requires it to be passed between rollers. These rollers tend to press the free ends of the tongues down toward the plate. After the heater has been finished it is necessary to bend the tongues outward again in order to permit terminal sleeves to be slipped over them for factory testing. In the packing and shipping of the plates it is likely that the tongues may accidentally be bent down again to such an extent that it will be necessary for the fabricator to bend them out to facilitate the application of the terminal sleeves. Additional bending of the tongues may also occur in the final assembly operation when the plate is installed in its frame by the fabricator.

' In accordance with this invention, my connectors are made so that bending forces applied to their tongues do not cause the damage that they did heretofore. The reason for this is that each tongue, in a location a short distance from the adjoining base, is reduced in cross sectional area to weaken the tongue materially at that point. It follows that when there is applied to the tongue pressure that might otherwise loosen the connector from the plate or cause it to fracture the surface of the glass, the pressure will bend the tongue without difficulty instead of being transmitted through the tongue to the connector base. There are various ways in which this reduction in cross sectional area can be accomplished. A simple and preferred way is to punch a hole 14 through the tongue when it is formed. This hole is near the inner end of the tongue, midway between its sides, and extends across the line where the body of the tongue is bent in the original forming operation. This hole may reduce the effective width of the tongue at that location by as much as a third, thereby assuring that if the tongue is bent again, it will bend along a line passing through the hole, which is at a point spaced from the junction of the base of the tongue with the glass plate. Of course, this reduction in the metal of the tongue allows it to bend much more easily then heretofore, so that the base of the connector will not fracture the glass.

the same effect can be obtained by forming notches 16 in the opposite edges of the tongue 17 at the same location, as shown in Fig. 5. These notches likewise reduce the width of the tongue at the desired point so that it will bend readily in that location and not disturb the base 18.

If the base 23; of the connector is made wider, as shown in Fig. 6, the inner end portion of the tongue 22 can be increased in width. The result will be that the tongue will always bend along the line where its narrow portion joins its wide portion.

In Fig. 7 the tongue 25 is weakened in a still different way, by reducing its thickness at 26 along a line extending across the inner end of the tongue a short distance from the base 27.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to repre sent its best embodiment. However, i desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An electrical connector adapted to connect an electric wire to an electric resistance element adhering to a glass plate, the connector comprising a metal base having an inner face adapted to be soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to said wire, the tongue having a free outer end and an inner end joined to the base, the tongue being reduced in cross sectional area a short distance from the base to weaken the tongue, whereby if pressure is applied to the tongue toward or away from the base it will bend the tongue at said reduced cross section instead of injuring the glass plate or separating said base therefrom.

2. An electrical connector adapted to connect an electric wire to an electric resistance clement adhering to a glass plate, the connector comprising a metal base having an inner face adapted to be soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to said wire, the tongue having a free outer end and an inner end joined to the base, the tongue being reduced in width at short distance from the base to weaken the tongue, whereby if pressure is applied to the tongue toward or away from the base it will bend the tongue across its reduced width instead of injuring the glass plate or separating said base therefrom.

3. An electrical connector adapted to connect an electric wire to an electric resistance element adhering to a glass plate, the connector comprising a metal base having an inner face adapted to be soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to said wire, the tongue having a free outer end and an inner end joined to the base, the tongue being provided with a hole located a short distance from the base to weaken the tongue, whereby it pressure is applied to the tongue toward or away from the base it will bend the "tongue along a transverse line passing through said hole instead of injuring the glass plate or separating said base therefrom.

4. An electrical connector adapted to connect an elec tric wire to an electric resistance element adhering to a glass plate, the connector comprising a metal base having an inner face adapted to be soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to said wire, the tongue having a free outer end and an inner end joined to the base, the opposite edges of the tongue a short distance from the base being provided with a pair of notches to weaken the tongue between N them, whereby if pressure is applied to the tongue toward Instead of placing a hole in the center of the tongue,

or away from the base it will bend the tongue along a transverse line joining said notches instead of injuring the glass plate or separating said base therefrom.

-5. An electrical connector adapted to connect an electric wire to an electric resistance element adhering to a glass plate, the connector comprising a metal base having an inner face adapted to be soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to said wire, the tongue having a free outer end and an inner end joined to the base, the tongue being bent transversely along a line a short distance from the base and being provided with a hole extending across said line to weaken the tongue along that line, whereby if pressure is applied to the tongue toward or away from the base it will bend the tongue along said line instead of injuring the glass plate or separating said base therefrom.

6. An electrical connector adapted to connect. an electric wire to an electric resistance element adhering to a fastened to said wire, the tongue. having a free outer end and an inner end joined to the base, the tongue being bent transversely along a line a short distance from the base and having notches in the edges of the tongue at opposite ends of said line, whereby if pressure is applied to the ton us toward or awa from the base it will bend the 5 tongue along said line instead of injuring the glass plate or separating said base therefrom.

7. The combination with a tempered glass plate and an electric resistance element adhering thereto, of an electrical connector comprising a metal base having an inner face soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to an electric wire, the tongue having a free outer end and an inner end joined to the base, the tongue being reduced in cross sectional area a short distance from the base to weaken the tongue, whereby if sufficient pressure is applied to the tongue toward or away from the base it will bend the tongue at said reduced cross section instead of injuring the glass plate or separating the connector base from said resistance element.

8. The combination with a tempered glass plate and an electric resistance element adhering thereto, of an electrical connector comprising a metal base having an inner face soldered to said element, and a struck-out integral tongue projecting from the outer face of the base adapted to slidably receive a sleeve fastened to an electric wire, the tongue having a free outer end and an inner end joined to the base, the tongue being provided With a hole located a short distance from the base to weaken the tongue and having a diameter equal to about one-third of the width of the tongue, whereby if suffieient pressure is applied to the tongue toward or away from the base it will bend the tongue along a transverse line passing through said hole instead of injuring the glass plate or separating the connector base from said resistance element.

References Cited in the file of this patent UNITED STATES PATENTS 1,647,474 Seymour Nov. 1, 1927 2,418,461 Becker et a1. Apr. 8, 1947 2,581,967 Mitchell Jan. 8, 1952 2,636,920 Lockery et a1. Apr. 28, 1953 2,644,066 Glynn June 30, 1953 

1. AN ELECTRICAL CONNECTOR ADAPTED TO CONNECT AN ELECTRIC WIRE TO AN ELECTRIC RESISTANCE ELEMENT ADHERING TO A GLASS PLATE, THE CONNECTOR COMPRISING A METAL BASE HAVING AN INNER FACE ADAPTED TO BE SOLDERED TO SAID ELEMENT, AND A STRUCK-OUT INTEGRAL TONGURE PROJECTING FROM THE OUTER FACE OF THE BASE ADAPTED TO SLIDABLY RECEIVE A SLEEVE FASTENED TO SAID WIRE, THE TONGUE HAVING A FREE OUTER END AND AN INNER END JOINED TO THE BASE, THE TONGUE BEING REDUCED IN CROSS SECTIONAL AREA A SHORT DISTANCE FROM THE BASE TO WEAKEN THE TONGUE, WHEREBY IF PRESSURE IS APPLIED TO THE TONGUE TOWARD OR AWAY FROM THE BASE IT WILL BEND TO THE TONGUE TOWARD OR AWAY FROM THE BASE IT WILL BEND THE TONGUE AT SAID REDUCED CROSS SECTION INSTEAD OF INJURING THE GLASS PLATE OR SEPARATING SAID BASE THEREFROM. 